• Title/Summary/Keyword: Refrigeration Cycle

Search Result 445, Processing Time 0.024 seconds

Thermodynamic Analysis of Re-liquefaction Cycle of LNG Boil-off Gas (LNG 증발기체의 재액화 사이클에 대한 열역학 해석)

  • Chin, Young-Wook;Moon, Jeong-Woo;Lee, Yoon-Pyo;Chang, Ho-Myung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.19 no.7
    • /
    • pp.485-490
    • /
    • 2007
  • The LNG BOG re-liquefaction system for LNG carriers was designed based on the Claude refrigeration cycle and the thermodynamic analysis was carried out in order to find the design point of the three heat exchangers constituting the system. The thermodynamic analysis revealed that the system state could be defined by the three cold endpoint temperatures of the three-pass heat exchanger. Hence the iso-lines of the specific liquefaction work, taken as the performance indicator, were presented in terms of those three temperatures and discussed. The system was found most economical when those three temperatures approached a single temperature of $-140^{\circ}C$ and thus this system state could be taken as the design point for the heat exchangers.

Exergy analysis of R717 high-efficiency OTEC power cycle for the efficiency and pressure drop in main components

  • Yoon, Jung-In;Son, Chang-Hyo;Yang, Dong-Il;Kim, Hyeon-Uk;Kim, Hyeon-Ju;Lee, Ho-Saeng
    • Journal of Power System Engineering
    • /
    • v.17 no.5
    • /
    • pp.52-57
    • /
    • 2013
  • In this paper, an analysis on exergy efficiency of high-efficiency R717 OTEC power system for the efficiency and pressure drop in main components were investigated theoretically in order to optimize the design for the operating parameters of this system. The operating parameters considered in this study include turbine and pump efficiency, and pressure drop in a condenser and evaporator, respectively. As the turbine efficiency of R717 OTEC power system increases, the exergy efficiency of this system increases. But pressure drop in the evaporator of R717 OTEC power system increases, the exergy efficiency of this system decreases, respectively. And, in case of exergy efficiency of this OTEC system, the turbine efficiency and pressure drop in a condenser on R717 OTEC power system is the largest and the lowest among operation parameters, respectively.

Optimization of Spray Nozzle, R-404A Charge Amount and Visualization of Ice Formation in a Residential Built-in Ice Maker (가정용 빌트인 제빙기의 분무 노즐, R-404A 충전량 최적화 및 제빙 가시화)

  • Kim, Nae-Hyun;Kim, Hyun-Jin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.29 no.8
    • /
    • pp.437-445
    • /
    • 2017
  • Because of improvement of living standards and increased use of ice at home, built-in ice makers are of interest. In this study, refrigeration cycle of a unitary ice maker for residential usage was optimized using R-404A. Optimization was achieved through a search for proper refrigerant charge amount. For the present ice maker producing ice for 24 cups, the optimum charge amount was 200 g. In this configuration, the ice making cycle time was 17 minutes 53 seconds, ice production was 1.27 kg/h and COP was 0.310. After initial start-up, condensation and evaporation temperatures gradually decreased with time. As ice builds in the cup, heat transfer performance of the evaporator decreases, that results in decrease of evaporation and condensation temperatures. Replacement of existing slit nozzles with individual circular hole nozzles improved ice production capacity by 10 percent. Through visualization of ice formation in the ice cup, growth rate of the ice in the cup was relatively uniform.

Performance Characteristics of a Hybrid Air-Conditioner for Telecommunication Equipment Rooms (통신기지국용 하이브리드 냉방기의 성능특성 연구)

  • Kim, Yong-Chan;Choi, Jong-Min;Kang, Hoon;Yoon, Joon-Sang;Kim, Young-Bae;Choi, Kwang-Min;Lee, Ho-Seong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.18 no.11
    • /
    • pp.874-880
    • /
    • 2006
  • The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was $8.3^{\circ}C$.

Optimum Size Combination of Heat Exchangers in a Small Gifford-Mchon/ Joule-Thomson Refrigerator (소형 Gifford-McMahon/Joule-Thomson 냉동기에서 열교환기의 최적 조합)

  • 김영률;이상용;장호명
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.16 no.11
    • /
    • pp.2196-2202
    • /
    • 1992
  • The optimum size combination of heat exchangers in a Joule-Thomson(J-T) circuit for small cryogenic systems has been sought analytically, when the circuit is combined with a two-stage Gifford-McMahon(GM) cooler. Full thermodynamic cycle analysis was carried out to predict the performance of the combined refrigeration system. Relevant convective heat transfer coefficients, the computerized properties of helium, and the refrigeration capacity curve of a typical GM cooler have been used in the analysis. The result showed that, by changing the configuration(heat exchanger area ratio) of the system, the performance of the commonly-used GM/J-T refrigerators could be optimized. For the maximum refrigeration performance, the optimum mass flow rate of the refrigerant and the relative size between the heat exchangers have been obtained, when the cooling load was 0.1W at 3.995K with the total heat exchanger area being given.

A Study of Lorentz-Meutzner's Two Evaporator Refrigeration System Using Alternative Refrigerant Mixtures (대체혼합냉매를 사용하는 Lorentz-Meutzner의 이중 증발기 냉동 시스템의 성능에 관한 연구)

  • Park, Y.M.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.4 no.2
    • /
    • pp.123-136
    • /
    • 1992
  • A preliminary thermodynamic design model of two-evaporator refrigerator/freezer system is constructed. This system is based on Lorentz-Meutzner cycle using refrigerant mixtures. This model screens alternative refrigerant (R32, R125, R143a, R22, R134a, R152a, R124, R142b, R123) mixtures to select the best performance-giving refrigerant mixtures and its composition for the system. Also, it estimates the effects of cooling temperatures of intercoolers, evaporator's area ratio, cooling load ratio on the performance of the system. The COP of the system ranges from 1.4 to 1.6, which is superior to that of the single evaporator system charged with R12 by 13% to 29%. Among 15 mixtures, R22/R123, R143a/R123, R32/R142b, and R32/R124 (in the order of high COP) are most recommendable. For the case of R22/R123, R22 mass fraction more than 0.5(Load Ratio=1.0) or 0.7(Load Ratio=0.33) is recomended in order to replace R12 without reduction in volumetric capacity when keeping the compressor as the same one. COP has the highest value with X(R22)=0.7 and 0.8, respectively. For the case of R143a/R123, in the similar manner, mass fraction of R143a is more than 0.5 or 0.6 while best performance occurs at X(R143a)=0.8. Higher temperature intercooler is more important for the performance of the system than lower temperature intercooler. The area ratio of evaporators is roughly proportional to load ratio of the evaporators.

  • PDF

A Study on the Minimization of the Refrigeration Power Consumptions Through the Determination of Demethanizer Top Pressure in the NGL Recovery Process Using Turbo-expander (터보 팽창기를 활용한 NGL 회수공정에서 최적의 탈메탄탑의 운전압력 결정을 통한 냉동 소요동력 최소화에 대한 연구)

  • Kim, Yu-Mi;Cho, Jung-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.12 no.2
    • /
    • pp.1032-1037
    • /
    • 2011
  • In this study, simulation and optimization works for a demethanizer column have been performed to obtain ethane and heavier products from a pretreated natural gas stream. Pretreated natural gas feed stream was partially condensed after being precooled by exchanging heat with demethanizer top vapor stream and by using an external refrigeration cycle with a propane refrigerant. Vapor stream was cooled further and partially condensed through a turbo-expander. The power generated from the expansion of turbo-expander was delivered to the compressor for the residue gas compression. Liquid stream was cooled by Joule-Thomson expansion valve and was fed to the middle section of the demethanizer. Recovery percent of ethane for feed natural was set to 80% and methane to ethane molar ratio was fixed as 0.0119. On the other hand, some of the cold heat could be recovered by splitting the feed stream and by exchanging heat with side reboiler in order to reduce the heat duty in the propane refrigeration cycle.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016 (설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.29 no.6
    • /
    • pp.327-340
    • /
    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

Optimization Study on the Performance Analysis of Organic Rankine Cycle for Characteristics of Low Temperature Heat Sources (저온열원의 특성에 따른 ORC 성능해석 최적화 연구)

  • Eom, Hong-Sun;Yoon, Cheon-Seog;Kim, Young-Min;Shin, Dong-Gil;Kim, Chang-Gi
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.24 no.1
    • /
    • pp.51-60
    • /
    • 2012
  • Optimization procedures of performance analysis for ORC(Organic Rankine Cycle) system are established to the characteristics of low temperature heat sources such as open-type and closed-type. Effective heat recovery and heat extraction related to maximum power of the cycle as well as heat quality and thermal efficiency must be considered in the case of the open-type low temperature heat source. On the other hand, in the case of the closed-type low temperature heat source, only thermal efficiency is important due to constant heat input. In this study, thermal efficiency and exergy efficiency representing a level of close to Carnot cycle are studied, as useful index for the optimization of the ORC system. To validate the results of cycle analysis, those are compared with appropriate experimental data of ORC system as a thermal efficiency point of view.

Simulation Study on the Performance Improvement of a $CO_2$ System Applying a Two-stage Phase-separate Cycle (2단압축 상분리 사이클을 적용한 이산화탄소 시스템의 성능향상에 관한 해석적 연구)

  • Ryu Chang-Gi;Lee Ho-Seong;Kim Yong-Chan;Cho Hong-Hyun;Cho Sung-Wook
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.18 no.8
    • /
    • pp.641-648
    • /
    • 2006
  • In this study, a two-stage phase-separate cycle was investigated analytically to improve the performance of the $CO_2$ system in the cooling mode. The simulation results were verified with the measured data. The predictions using the simulation model were consistent with the measured data within ${\pm}20%$ deviations. The performance of the modified $CO_2$ system with the two-stage phase-separated cycle was analyzed with the variations of outdoor temperature and EEV opening. The cooling COP decreased with the increase of compressor frequency. The highest COP was 2.7 at compressor frequencies of 30 Hz and 30 Hz for the first and second compressors, respectively. In addition, the cooling COP increased by 9.3% with an application of optimum control of the first and second-stage EEV openings.